I can think of two possible reason leading to the described behavior:
- If your site is deployed in a load balanced environment, but the servers in it are not configured properly to keep the controls' resources in the session. If this is the case, please, refer the following blog post explaining in details all configurations that need to be made in a WebFarm/WebGarden scenario in order for the resources for our controls to be loaded properly after each request:
- If for some reason the application does not have enough permissions to access problematic image files when accessed from the mentioned Windows 2012 server. You can try enabling the CDN for the page holding the Editor and see whether loading the controls' resources from there will make a difference:
- ScriptManager CDN
- StyleSheetManager CDN
Do you need help with upgrading your ASP.NET AJAX, WPF or WinForms projects? Check the Telerik API Analyzer
and share your thoughts.